Bobbin thread pull-off for sewing machines



Jan. 5, 1965 s. J. KETTERER 3,164,113

BOBBIN THREAD PULL-OFF' FOR SEWING MACHINES Filed May 14, 1963 2 Sheets-Sheet l ATTORNEY Jan. 5, 1965 s. J. KETTERER 3,164,113

BoBBIN THREAD PULL-OFF FOR SEWING MACHINES Filed May 14, 1963 2 Sheets-Sheet 2 INVENTOR. STANLEY J. KETTERER I BY WITNESS 6 5 L Z 'TTORNEY United States Patent O 7 3,164,113 BOBBIN THREAD PULL-OFF FR SEWlNG MACHINES Stanley l. Ketterer, Morris Plains, NJ., assignor to The Singer Company, a cnr-poration of New Jersey Filed May 14, 1963, Ser. No. 280,281 6 Claims. (Cl. 112-242) This invention relates to improvements in sewing machines employing a rotary loop taker complemental to a reciprocatory thread carrying needle in the formation of lock-stitches, the invention being particularly related to mechanism for metering under or locking thread from a thread carrying bobbin in the sewing machine loop taker during the formation of lock stitches.

It is an object of this invention to provide a bobbin thread pull-off device so organized relatively to a rotary loop taker of a lock stitch sewing machine as to inlluence the delivery of under or locking thread to the stitched seam in uniform manner regardless of the length of the stitches being formed.

It is also an object of this invention to provide in combination with stitch forming instrumentalities in which the bobbin rotation is frictionally restrained to apply bobbin thread tension of a bobbin thread pull-off device operative to supply bobbin thread to the stitched seam at substantially uniform tension regardless of the amount of thread wound on the bobbin.

Another object of this invention is to provide a bobbin thread pull-olf device which is compact and may be accommodated in the limited space available adjacent to the stitch forming instrumentalities of a sewing machine of the type employing a Vertical axis loop taker.

With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. l is a vertical cross sectional view of a sewing machine having this invention applied thereto,

FIG. 2 is an enlarged vertical cross sectional view of a portion of the sewing machine bed taken substantially along line 2^*2 of FIG. l, including a representation of the needle and bobbin threads, with the parts illustrated at the setting of a stitch,

FIG. 3 is a vertical cross sectional view similar to FIG. 2 with the parts illustrated as the needle begins to descend after the preceding stitch has been set, and illustrating the pull-olf member drawing thread from the bobbin,

FIG. 4 is an enlarged top plan view of a portion of the sewing and work feeding mechanism in the bed of the sewing machine of FIG. l, and

FIG. 5 is a perspective view of the bobbin thread pulloif member of this invention.

As illustrated in FIG. l of the drawings, the sewing machine to which this invention is applied includes a frame having a bed 11 formed with a work supporting surface 12, a standard 13 rising from the bed, and a bracket arm 14 extending from the standard and terminating in a sewing head 15. A thread carrying needle 16, which is endwise reciprocable in the sewing head, cooperates in the formation of lock stitches with a loop taker 17 journaled for rotation about a vertical axis in a bearing 18 in the bed. The needle is drivingly connected to a main shaft 19 journaled in the bracket arm so as to be reciprocated once for each rotation of the main shaft. By means of the bevel gear sets 2t), 21 and 22, a shaft 23 in the standard, a bed shaft 24, and a loop taker shaft 25, the loop taker is imparted two revolutions for each reciprocation of the needle and this 3,164,113 Patented Jan. 5, 1965 ICC geared actuating mechanism provides for the precise timed relationship between the needle and the loop-taker as is required for lock stitch formation.

Also carried on the sewing head 15 is a needle thread take up 27 driven by the main shaft 19 for manipulating the needle thread during sewing, as well as a spring loaded presser foot 28 which is biased downwardly against a throat plate 29 set into the work supporting surface 12 of the bed. The throat plate is formed with an aperture 36 to accommodate the endwise reciprocating needle and with slots 31 through which a feed dog 32 works in opposition to the presser foot 28 to transport work fabrics in stitching.

The work feeding mechanism is of the type referred to in the art as a four motion drop feed mechanism in that the feed dog is lifted and lowered into engagement with fabrics beneath the presser foot and advanced and returned along the line of feed, the feed dog being dropped beneath the upper level of the throat plate during the return motion. To this end, the feed dog is secured to a feed bar 33 which is pivoted on a stud 34 extending between upstanding rock arm 35 of a feed advance rock shaft 36 journaled in the bed. A rock arm 37 extending from the feed advance rock shaft is pivoted to a bifurcated pitman 38 in the standard which embraces a feed advance cam 39 fast on the main shaft 19. A Stitch length adjusting lever arm 40 extends from a slotted guide member 41 fulcrumed in the standard and embracing a slide block 42 pivoted on the pitman 3S.

The feed bar, beneath the feed dog is formed with a depending limb 43 to the lower extremity of which is pivoted a link 44 which depends from a rock arm 45 extending substantially horizontally from a feed lift rock shaft 46 journaled in the bed. A rock arm 47 on the feed lift rock shaft 46 is pivoted to a pitman 48 in the standard which embraces a feed lift eccentric 49 fast on the main shaft 19.

Referring to FIGS. 2, 3 and 4, the loop taker 17 includes a cup shaped body portion 60 having a peripheral bearing rib 61 and with a loop seizing beak 62 formed thereon. A bobbin case 63 is formed with a bearing raceway 64 and is sustained with the raceway embracing the loop taker bearing rib 61 by means of a retractable keeper 65 on the bed having a spring 66 which occupies a position opposite an abutment surface 67 on the bobbin case. The keeper 65 also serves to restrain the bobbin case from rotation with the loop taker. Counter rotation of the bobbin case is prevented by a rotation restraining finger 68 on the bed which engages on abutment projection 69 on the bobbin case.

The bobbin case 63 is formed with an annular seat 70 which accommodates the upper llange 71 of a thread carrying bobbin 72. Formed axially of the bobbin in the upper flange is a spherical depression 73 which accommodates a spherical projection 74 formed on a bobbin hold-down arm 75 pivoted on the bobbin case and biased downwardly by a spring 76 to apply a normal force between the bobbin flange 71 and the bobbin case seat 70 frictionally to resist turning of the bobbin thereby to provide a tension on the bobbin thread during sewing when the stitches are being set.

The bobbin case adjacent to the path of needle reciprocation is formed with van inclined bobbin thread accommodating slot 77 through which thread may be directed onto the bobbin. The slot is spanned internally of the bobbin case by a cross piece 7 S. During sewing, .the path of the bobbin thread from the bobbin to the work passes beneath the cross piece 7S and over an inclined surface 79 on the bobbin case 63 adjacent to the slot 77.

The bobbin thread pull-olf member 96 of this invention is illustrated in place in the sewing machine in FIGS. 2, 3

alegria and 4 and a detached View is illustrated 'in FIG. 5. The pull-olf member 9% preferably comprises an integral sheet metal stamping including a flat horizontal portion 9i adapted to overlie the feed bar and formed with elongate .off member slidably in place. vl5`orwardly of the feed bar the pull-off member is formed with an aperture 94 to accommodate endwise reciprocation of the needle and through which aperture the bobbin thread is directed as it passes from the bobbin case to the thro-at plate needle aperture 3i). The rib 95 at the forward extremity of the pull-off member and across the apenture 9d thereof thus overlies the bobbin thread which extends from the bobbin to the work being stitched as illustrated in FIGS. 2 and 3` At the rear extremity the flat horizontal portion 91 of the pull-off member is joined by a vertical portion including a downwardly extending limb 96 and a rearwardly extending limb 97 which is bifurcated as at g3 and slidably embraces the stud 34 by which the feed bar is pivotally connected to the rock arm 36 of the feed advance rock shaft. The pull-off member 90 is thus constrained at both the front and rear for movement vertically with the feed bar 33 4but is mounted by the guide slot 92 and bifurcation g8 for freedom to slide relatively to the feed bar in the direction of the advance and return feed motions.

The pull-off member 9i) is imparted motion in the direction of the yadvance and return feed motion independently of the feed bar motion in this direction by means of a drive link Q9 pivotally -connected by a shouldered clamp screwlliid which may be adjustably secured in an elongate slot lill formed in the lower extremity of the downwardly extending limb 96 of the pull-olf member. The drive link 9i) is pivottally connected to a rock arm 1&2 depending from the feed lift rock shaft 46. The drive link 99 is preferably arranged inclined forwardly and downwardly from the pull-oft^ lmember limb 96 to the rock arm 102 as illustrated in FIG. 2. Since the feed lift motion imparted to theV feed bar by way of the Vfeed lift rock arm is substantially of constant amplitude regardless of stitch length adjustments, the motions imparted to the pull-off member 9@ will similarly be of substantially constant amplitude and this includes not only those components of the pull-off motion which are irnparted because the pull-ohc member shares the feed lift f motion of the feed bar, butvals'o thosey components of the pull-off motion in theV direction of the feed advance and return motion which are imparted by the drive link 99 from the feed ylift rock shaft.

FIGS. 2 and 3 indicate the preferred timing of the Vmotion of the pull-ofi member 9i) and illustrate the manner in which the pull-off member serves to meter bobbin thread to the seam.

FlG. 2 'indicates the position of parts at the completion of a stitch and at the completion of a feed advance stroke of the feed bar. The combined action of the setting of Y the previous stitch by the needle thread take up 27 and the transport of the work fabric to the left by the feed dog will have drawn the bobbin thread taut. After the stitch has been set and as the feed lift rock shaft do is oscillated clockwise as viewed in FIGS. 2 and 3 to drop the feed dog preparatory to its return motion, the pull-ntf member will be lowered with the feed bar and by virtue of the rock arm im and link 99 Will also be shifted to the left relatively to the feed bar into the position illustrated in FIG. 3 in which the rib 95 will act on the bobbin thread extending between the bobbin case 63 and the needle aperture 3 6 in the throat plate to draw a supply of thread from the bobbin for use in the succeeding stitch. The pull-ot member will be shifted upwardly and forwardly as the needle penetration and the formation of the succeeding stitch progresses, thus giving up the increment of bobbin `thread which had been pulled from the bobbin.

The pulloif device of this invention is particularly advantageous in its cooperation with a loop taker in which frictional resistance to turning of the bobbin is used to deveiop the bobbin thread tension. Since the thread is drawn from the bobbin in periodic increments during stitching, the tension which is applied by the turning of the bobbin varies during the withdrawal of each increment, initially rising to a peak as the bobbin is accelerated and then tapering off as the remainder of each increment is drawn from the bobbin. The pull-od device of .this invention is preferably' adjusted to draw from the bobbin slightly less than lan amount of bobbin thread necessary to form a short stitch. When the work feeding mechanism and the needie thread take up begin to draw the stitch into a work fabric therefore, it is the slack bobbin thread provided by the pull-olf device which is first encountered. Cniy near completion of the setting of each stitch by the take up 27 is thread drawn directly from the bobbin. The peak bobbin thread tension provided by the frictional resistance to turning of the bobbin is thus timed to coincide more closely with the actual stitch setting when the pull-Off device of this invention is used. Since this peak tension provided by a rotary bobbin thread tension is less subject to variation than the tension applied at any other 4point of thread withdrawal from the bobbin, a more uniformly set seam of stitches results from the combination of this invention. In particular, uniformly set stitches may be obtained from `a full to an empty bobbin when this invention is employed.

Having thus described the nature of the invention, what i claim herein is:

l. in a lockstitch sewing machine having stitch forming instrumentalities including a thread carrying needle, a loop taker carrying a supply of under thread and cooperating with said needle in the formation of lock stitches, and a drop feed mechanism including a feed bar, means for imparting advance and return movements to said feed bar and means for imparting rising and falling movements to said feed bar, and under thread pull-oil mechanism comprising a thread pull-off member, under thread engaging means on said thread pull-off member, means supporting said thread puh-off member on said feed bar for rising and falling movement therewith and for movement relatively thereto in the direction of said feed bar advance and return movements. and mechanism operating in timed relation with said stitch forming instrumentalities for shifting said thread pull-off member relatively to said feed bar.

2. In a lockstitch sewing machine having stitch forming instrumentalities including a thread carrying needle, a loop taker carrying `a lsupply of under thread vand cooperating with said needle in the lformation of lock stitches, and a drop feed mechanism inciuding a lfeed bar, means for imparting advance and return movements to said feed bar and means for imparting rising .and lfalling movements to .said ,feed bar, an under thread pull-off mechanism comprising `a thread pull-off member, under thread engaging means on `said thread puli-off member, means supporting said thread pull-off member on said feed lbar for rising and falling movement therewith and for movement relatively thereto in vthe direction of said lfeed bar 'advance and return movements, and a linkage operatively connecting said thread .pull-oit member with said means for imparting rising and falling movements to said feed bar for shifting said thread pull-off mem-ber relatively to said feed bar.

3. vIn a lockstitch sewing machine having sitch forming linstrmnentalities including a thread carrying needle, a loop taker carrying a supply of under thread Iand cooperating with said needle in the formation of lock stitches, and a drop feed mechanism including a feed dog extending between said needle and said loop taker, means for imparting advance and return movements to `said feed dog, means for :imparting rising and Ifalling movements ato feed dog, an under thread pull-off mechanism comprising a thread 4pull-off member, under thread engaging means on said thread pull-off member, means supporting said thread pull-off member for movement relatively to said feed dog in the direction of advance and return motion of said feed dog and with said under thread engaging means on said thread pull-off member disposed `biet-Ween said 'feed dog and said loop taker, and mechanism operated by said means for imparting rising `and falling movements to said feed dog for shifting said Thread pull-off member -relatively to said feed dog.

4. In a lockstitch sewing machine having stitch forming instrumentalities including a thread carrying needle, a loop taker carrying a supply `of under thread and cooperating with said needle in Ithe formation of lock stitches, and a drop -feed mechanism including a feed bar supported for movement in a substantially vertical plane, means for -irnparting -advance and return movements to said -feed bar and means for imparting rising and falling movements to said feed bar, an under thread pull-off mechanism comprising a thread pull-off member, under thread engaging means on said thread pull-off member, means supporting said thread pull-off member on said feed bai for rising and falling movement therewith and for movement relatively thereto in the direction of said feed bar advance and return movements, an `oscillating drive element for said thread pull-off member .supported in said sewing machine for oscillation lin a plane parallel'to the vertical plane of movement of the feed fbar and driven in timed relation with said stitch Iforming instrumentalities, and a connecting link .pivoted to said oscillating drive element and to said thread pull-off member, said connecting link being disposed in a plane substantially parallel to said vertical plane of movement of said -feed bar and extending from said oscillating drive element upwardly and in the advance direction of the -feed bar toward the connection with said thread pull-off member.

`5. In a lockstitch sewing machine having stitch forming instrumentalities including a thread carrying needle, a loop taker carrying a supply of under thread and cooperating with said needle in the formation of lock stitches, and a drop feed mechanism includ-ing a feed bar supported for movement in a substantially vertical plane, means for imparting advance and return movements to said feed bar, a feed lift rock shaft journaled in said sewing machine, a feed lift rock arm fast on said rock shaft and operatively connected to said feed bar to impart rising and falling movements thereto, an -under thread pull-off mechanism comprising a thread pull-off member, under thread engaging means on said thread pull-off member, means supporting said thread pull-off mem-'ber on said feed bar for rising and falling movement therewith and for movement `relatively thereto in the direction Iof said feed bar advance :and return movements, a thread pull-olf actuating rock arm fast on said feed lift rock shaft, and a connecting link pivoted to said thread pull-off actuating rock arm and to said thread pull-olf member, said connecting 4link lbeing disposed in a plane substantially parallel to said vertical plane of movement of said lfeed bar and extending from said thread pull-off actuating rock arm upwardly and in the advance direction of the feed lbar `toward the connection with said thread pull-off member.

6. In a lockstitch sewing machine having stitch forming instrumentalities including a thread carrying needle, a loop taker carrying a supply of under thread and cooperating with said needle in lthe formation of lock stitches, and a drop feed mechanism including a feed ibar sup-ported for movement in a substantially vertical plane, means for mparting advance and return movements to said feed bar, and under thread pull-off mechanism comprising .a thread pull-off member, underV thread engaging means on said thread pull-off member, means `supporting said thread pulloff member on said feed bar for rising and falling movement therewith and for movement relatively thereto in the direction of said feed bar advance and return movements, a feed lift rock `arm fast on said feed lift rock shaft, an

actuating rock arm for .said thread pull-off member fast v on said feed lift rock shaft, a -pivoted connecting link depending from said feed lift rock arm Ito said feed bar, and a pivoted connecting link depending from said thread pullyoff member to said thread pull-off actuating rock arm.

References Cited in the file of this patent UNITED STATES PATENTS 723,313() Steward Mar. 24, 19013 875,613' `Parkes Dec. 31, 1907 927,993 `Mills July 13, 1909 1,792,237 Parkes Feb. 10, 1931 V2,555,658 Ritter June 5, 1951 2,888,892 lKestell et al. J-une 2, 11959 2,966,130 Johnson 'Dec. 27 196.0 

1. IN A LOCKSTITCH SEWING MACHINE HAVING STITCH FORMING INSTRUMENTALITIES INCLUDING A THREAD CARRYING NEEDLE, A LOOP TAKER CARRYING A SUPPLY OF UNDER THREAD AND COOPERATING WITH SAID NEEDLE IN THE FORMATION OF LOCK STITCHES, AND A DROP FEED MECHANISM INCLUDING A FEED BAR, MEANS FOR IMPARTING ADVANCE AND RETURN MOVEMENTS TO SAID FEED BAR AND MEANS FOR IMPARTING RISING AND FALLING MOVEMENTS TO SAID FEED BAR, AND UNDER THREAD PULL-OFF MECHANISM COMPRISING A THREAD PULL-OFF MEMBER, UNDER THREAD ENGAGING MEANS ON SAID THREAD PULL-OFF MEMBER, MEANS SUPPORTING SAID THREAD PULL-OFF MEMBER ON SAID FEED BAR FOR RISING AND FALLING MOVEMENT THEREWITH AND FOR MOVEMENT RELATIVELY THERETO IN THE DIRECTION OF SAID FEED BAR ADVANCE AND RETURN MOVEMENTS, AND MECHANISM OPERATING IN TIMED RELATION WITH SAID STITCH FORMING INSTRUMENTALITIES FOR SHIFTING SAID THREAD PULL-OFF MEMBER RELATIVELY TO SAID FEED BAR. 